The present invention relates generally to the abatement of contaminant laden industrial process emissions and more particularly, to a system which utilizes a regenerative catalytic oxidizer (RCO) to perform the abatement process.
Regenerative catalytic oxidizers recover and transfer heat remaining in the cleansed exhaust gas to emissions entering the oxidizer thereby minimizing the amount of supplemental energy required to raise the emission to its ignition temperature. Characteristically, flow control valves are used to direct the emissions to one or more regenerators for preheating prior to thermal or catalytic oxidation.
Industrial process emissions typically contain particulates and major gaseous air pollutants such as volatile organic compounds (VOCs), nitrogen oxides (NO.sub.x) and carbon monoxide (CO), all of which contaminate the environment when vented to the atmosphere. Regenerative catalytic oxidizers (RCO) utilize a catalytic material to effect oxidation of the VoCs and CO at lower peak temperatures than, for example, treatment by thermal oxidation. The catalytic material is located in the higher temperature zones of the RCO, adjacent to a combustion chamber wherein a burner or supplementary heat source is used to heat the catalyst. An RCO also utilizes heat storage media, usually located in the lower temperature zones at the gas entrance and exit ports, thereby facilitating fluid heat transfer as the heated gas is passed through.
The system typically consists of multiple beds of heat storage and catalyst materials. These beds are connected to a common chamber where a heater, such as a burner, is utilized to heat the gas to the desired operating temperature, normally in the range of 600.degree. F. (.apprxeq.315.degree. C.) to 1000.degree. F. (.apprxeq.540.degree. C.), thereby effecting catalytic conversion of the VOCs, and CO, and producing water and CO.sub.2.
As the catalyst becomes aged due to repeated reaction of gases, the exhausted catalyst must either be regenerated or be replaced. Shape is critical when considered in a maintenance context. If regenerative cleaning is a design consideration, random catalysts such as spherical or saddle shaped catalytic particles are preferred. The commonly designed honeycomb configuration is not readily regenerated by water or other cleaning agents given the entrainment of these fluids due to blockages within the catalytic bed.
RCOs generally utilize a vertical orientation of components resulting in vertical flow in and out of the reactor. Such vertical orientation is less than desirable for several reasons. Due to channeling and inefficient utility related to a vertical emission flow regime, a vertically orientated RCO must be significantly sized per cubic foot of process emissions treated. In addition, because the catalyst is generally disposed immediately above the heat media, percolation of the catalytic material through the heat media can cause blockages and inefficient heat exchange within the heat exchange bed. Furthermore, again due to possible heat media contamination, the vertical design makes catalyst regeneration, or removal and replacement, difficult.